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Sum of divisors of 4*n-2 of form 4*k+3.
1

%I #49 Jul 08 2023 08:04:55

%S 0,3,0,7,3,11,0,18,0,19,10,23,0,30,0,31,14,42,0,42,0,43,18,47,7,54,0,

%T 66,22,59,0,73,0,67,26,71,0,93,18,79,30,83,0,90,0,98,34,114,0,113,0,

%U 103,60,107,0,114,0,138,42,126,11,126,0,127,46,131,26,180,0,139,50,154,0,157,0,151,54,186,0,162,30

%N Sum of divisors of 4*n-2 of form 4*k+3.

%F a(n) = A050452(4*n-2).

%F G.f.: Sum_{k>0} (4*k-1) * x^(2*k) / (1 - x^(4*k-1)).

%t a[n_] := DivisorSum[4*n - 2, # &, Mod[#, 4] == 3 &]; Array[a, 100] (* _Amiram Eldar_, Jul 08 2023 *)

%o (PARI) a(n) = sumdiv(4*n-2, d, (d%4==3)*d);

%Y Cf. A050452, A359290, A363259.

%K nonn

%O 1,2

%A _Seiichi Manyama_, Jul 08 2023